TheBeagle, in her homeward voyage, touched at New Zealand, Australia, Van Diemen's Land, and the Cape of Good Hope. In order to confine the third Part of these Geological Observations to South America, I will here briefly describe all that I observed at these places, worthy of the attention of geologists.

New South Wales.—My opportunities of observation consisted of a ride of ninety geographical miles to Bathurst, in a W.N.W. direction from Sydney. The first thirty miles from the coast passes over a sandstone country, broken up in many places by trap-rocks, and separated by a bold escarpement overhanging the river Nepean, from the great sandstone platform of the Blue Mountains. This upper platform is 1000 feet high at the edge of the escarpement, and rises in a distance of 25 miles to between 3000 and 4000 feet above the level of the sea. At this distance, the road descends to a country rather less elevated, and composed in chief part of primary rocks. There is much granite, in one part passing into a red porphyry with octagonal crystals of quartz, and intersected in some places by trapdikes. Near the Downs of Bathurst, I passed over much pale-brown, glossy clay-slate, with the shattered laminæ running north and south: I mention this fact, because Captain King informs me, that in the country a hundred miles southward, near Lake George, the mica-slate ranges so invariably north and south, that the inhabitants take advantage of it in finding their way through the forests.